The steel process step by step

Once the material has been melted and is in liquid form at high temperature, dry additives are added. Due to the high temperature, the addition of liquids is not possible, as this would pose a risk of vapour explosion. In this process step, ceramic ventilate, hoses and tube which are designed to withstand heavy abrasive wear and high thermal stresses.

The steel refining process

Transport and storage of acids

For the internal transport of acids from the raw acid station mainly centrifugal pumps. Magnetic drive pumps are particularly recommended for safety reasons, as they are leak-free. From the raw acid station, the acids are usually pumped to a mixing tank. For this purpose, we can offer different types of tanks, such as dual laminate tanks, These are fibreglass tanks with an internal polymer liner that provides high corrosion resistance. These are also referred to as lined tanks. When handling hydrofluoric acid (HF), for example, fibreglass is generally avoided. In such cases, tanks made of homogeneous polymer materials, such as HDPE (high molecular weight polyethylene), are recommended instead. For these mixing tanks, static mixers used.

We sell plastic valves made of PP and PVDF for these applications. In cold outdoor environments, we recommend fluoroplastic lined steel valves as these valves can withstand temperatures between -60 and 200 degrees C. In environments with acids, the air is corrosive and needs to be ventilated. This is done with the help of GRP pipes, GRP fans and larger dampers made of various polymeric materials.

prayer bath

Different acids are used depending on the type of steel to be pickled. When pickling carbon steel, hydrochloric or sulphuric acid is usually used. For stainless steels, such as AISI 304, and acid-resistant steels, such as AISI 316L, a mixture of, for example, 5 % hydrofluoric acid (HF) and 20-25 % nitric acid (HNO₃) is used. Pickling baths can be made of glass fibre reinforced plastic (GRP). Pickling baths are heated using heat exchangers, where we can offer both plastic and graphite heat exchangers that can be used depending on the process requirements.

The pumps we recommend are shaft-sealed centrifugal pumps. Due to the metal particles, it is not possible to use magnetic drive pumps. In the environment around the pickling bath, we can also offer grating and load-bearing construction that can withstand the corrosion environment made of fibreglass, GRP. In combination with pickling baths, the choice of valves depends on the temperature. For the regeneration stage that comes when the pickling sludge is emptied, we mainly use lined centrifugal pumps.

Acid neutralisation department

In the acid neutralisation section, which follows the regeneration, lime is used to neutralise the acid back to pH 7. If dry lime is used, it is handled via a hose system in combination with a dispatch vessel. When neutralising milk of lime, a dynamic mixer is used in the lime mixing vessel.

Pumping milk of lime requires continuous flushing to avoid clogging of the equipment, which is done using a so-called quench tank. The valves used in this step are usually hose valves, which at neutral pH values can be made of natural rubber.

Filter press

The sludge resulting from neutralisation is sent to a chamber filter press. To transport the sludge, it is not possible to use a normal centrifugal pump, but instead a filter press pump with 14-15 bar outlet pressure is used.

The internal treatment plant

This step includes flocculation and sludge management, where both dosing pumps and for example hose pumps used.